Documentation/filesystems/proc.txt: improve smaps field documentation

[pandora-kernel.git] / Documentation / keys-request-key.txt

diff --git a/Documentation/keys-request-key.txt b/Documentation/keys-request-key.txt
index 5f2b9c5..09b55e4 100644 (file)
--- a/Documentation/keys-request-key.txt
+++ b/Documentation/keys-request-key.txt
@@ -3,15 +3,38 @@
                              ===================
 
 The key request service is part of the key retention service (refer to
                              ===================
 
 The key request service is part of the key retention service (refer to

-Documentation/keys.txt). This document explains more fully how that the
-requesting algorithm works.
+Documentation/keys.txt).  This document explains more fully how the requesting
+algorithm works.

 
 The process starts by either the kernel requesting a service by calling
 
 The process starts by either the kernel requesting a service by calling

-request_key():
+request_key*():

 
        struct key *request_key(const struct key_type *type,
                                const char *description,
 
        struct key *request_key(const struct key_type *type,
                                const char *description,

-                               const char *callout_string);
+                               const char *callout_info);
+
+or:
+
+       struct key *request_key_with_auxdata(const struct key_type *type,
+                                            const char *description,
+                                            const char *callout_info,
+                                            size_t callout_len,
+                                            void *aux);
+
+or:
+
+       struct key *request_key_async(const struct key_type *type,
+                                     const char *description,
+                                     const char *callout_info,
+                                     size_t callout_len);
+
+or:
+
+       struct key *request_key_async_with_auxdata(const struct key_type *type,
+                                                  const char *description,
+                                                  const char *callout_info,
+                                                  size_t callout_len,
+                                                  void *aux);

 
 Or by userspace invoking the request_key system call:
 
 
 Or by userspace invoking the request_key system call:
 


@@ -20,16 +43,30 @@ Or by userspace invoking the request_key system call:
                                 const char *callout_info,
                                 key_serial_t dest_keyring);
 
                                 const char *callout_info,
                                 key_serial_t dest_keyring);
 

-The main difference between the two access points is that the in-kernel
-interface does not need to link the key to a keyring to prevent it from being
-immediately destroyed. The kernel interface returns a pointer directly to the
-key, and it's up to the caller to destroy the key.
+The main difference between the access points is that the in-kernel interface
+does not need to link the key to a keyring to prevent it from being immediately
+destroyed.  The kernel interface returns a pointer directly to the key, and
+it's up to the caller to destroy the key.
+
+The request_key*_with_auxdata() calls are like the in-kernel request_key*()
+calls, except that they permit auxiliary data to be passed to the upcaller (the
+default is NULL).  This is only useful for those key types that define their
+own upcall mechanism rather than using /sbin/request-key.
+
+The two async in-kernel calls may return keys that are still in the process of
+being constructed.  The two non-async ones will wait for construction to
+complete first.

 
 The userspace interface links the key to a keyring associated with the process
 to prevent the key from going away, and returns the serial number of the key to
 the caller.
 
 
 
 The userspace interface links the key to a keyring associated with the process
 to prevent the key from going away, and returns the serial number of the key to
 the caller.
 
 

+The following example assumes that the key types involved don't define their
+own upcall mechanisms.  If they do, then those should be substituted for the
+forking and execution of /sbin/request-key.
+
+

 ===========
 THE PROCESS
 ===========
 ===========
 THE PROCESS
 ===========


@@ -40,8 +77,8 @@ A request proceeds in the following manner:
      interface].
 
  (2) request_key() searches the process's subscribed keyrings to see if there's
      interface].
 
  (2) request_key() searches the process's subscribed keyrings to see if there's

-     a suitable key there. If there is, it returns the key. If there isn't, and
-     callout_info is not set, an error is returned. Otherwise the process
+     a suitable key there.  If there is, it returns the key.  If there isn't,
+     and callout_info is not set, an error is returned.  Otherwise the process

      proceeds to the next step.
 
  (3) request_key() sees that A doesn't have the desired key yet, so it creates
      proceeds to the next step.
 
  (3) request_key() sees that A doesn't have the desired key yet, so it creates


@@ -56,31 +93,34 @@ A request proceeds in the following manner:
  (4) request_key() then forks and executes /sbin/request-key with a new session
      keyring that contains a link to auth key V.
 
  (4) request_key() then forks and executes /sbin/request-key with a new session
      keyring that contains a link to auth key V.
 

- (5) /sbin/request-key execs an appropriate program to perform the actual
+ (5) /sbin/request-key assumes the authority associated with key U.
+
+ (6) /sbin/request-key execs an appropriate program to perform the actual

      instantiation.
 
      instantiation.
 

- (6) The program may want to access another key from A's context (say a
-     Kerberos TGT key). It just requests the appropriate key, and the keyring
+ (7) The program may want to access another key from A's context (say a
+     Kerberos TGT key).  It just requests the appropriate key, and the keyring

      search notes that the session keyring has auth key V in its bottom level.
 
      This will permit it to then search the keyrings of process A with the
      UID, GID, groups and security info of process A as if it was process A,
      and come up with key W.
 
      search notes that the session keyring has auth key V in its bottom level.
 
      This will permit it to then search the keyrings of process A with the
      UID, GID, groups and security info of process A as if it was process A,
      and come up with key W.
 

- (7) The program then does what it must to get the data with which to
+ (8) The program then does what it must to get the data with which to

      instantiate key U, using key W as a reference (perhaps it contacts a
      Kerberos server using the TGT) and then instantiates key U.
 
      instantiate key U, using key W as a reference (perhaps it contacts a
      Kerberos server using the TGT) and then instantiates key U.
 

- (8) Upon instantiating key U, auth key V is automatically revoked so that it
+ (9) Upon instantiating key U, auth key V is automatically revoked so that it

      may not be used again.
 
      may not be used again.
 

- (9) The program then exits 0 and request_key() deletes key V and returns key
+(10) The program then exits 0 and request_key() deletes key V and returns key

      U to the caller.
 
      U to the caller.
 

-This also extends further. If key W (step 5 above) didn't exist, key W would be
-created uninstantiated, another auth key (X) would be created [as per step 3]
-and another copy of /sbin/request-key spawned [as per step 4]; but the context
-specified by auth key X will still be process A, as it was in auth key V.
+This also extends further.  If key W (step 7 above) didn't exist, key W would
+be created uninstantiated, another auth key (X) would be created (as per step
+3) and another copy of /sbin/request-key spawned (as per step 4); but the
+context specified by auth key X will still be process A, as it was in auth key
+V.

 
 This is because process A's keyrings can't simply be attached to
 /sbin/request-key at the appropriate places because (a) execve will discard two
 
 This is because process A's keyrings can't simply be attached to
 /sbin/request-key at the appropriate places because (a) execve will discard two


@@ -116,17 +156,17 @@ A search of any particular keyring proceeds in the following fashion:
 
  (2) It considers all the non-keyring keys within that keyring and, if any key
      matches the criteria specified, calls key_permission(SEARCH) on it to see
 
  (2) It considers all the non-keyring keys within that keyring and, if any key
      matches the criteria specified, calls key_permission(SEARCH) on it to see

-     if the key is allowed to be found. If it is, that key is returned; if
+     if the key is allowed to be found.  If it is, that key is returned; if

      not, the search continues, and the error code is retained if of higher
      priority than the one currently set.
 
  (3) It then considers all the keyring-type keys in the keyring it's currently
      not, the search continues, and the error code is retained if of higher
      priority than the one currently set.
 
  (3) It then considers all the keyring-type keys in the keyring it's currently

-     searching. It calls key_permission(SEARCH) on each keyring, and if this
+     searching.  It calls key_permission(SEARCH) on each keyring, and if this

      grants permission, it recurses, executing steps (2) and (3) on that
      keyring.
 
 The process stops immediately a valid key is found with permission granted to
      grants permission, it recurses, executing steps (2) and (3) on that
      keyring.
 
 The process stops immediately a valid key is found with permission granted to

-use it. Any error from a previous match attempt is discarded and the key is
+use it.  Any error from a previous match attempt is discarded and the key is

 returned.
 
 When search_process_keyrings() is invoked, it performs the following searches
 returned.
 
 When search_process_keyrings() is invoked, it performs the following searches


@@ -138,8 +178,8 @@ until one succeeds:
 
  (3) The process's session keyring is searched.
 
 
  (3) The process's session keyring is searched.
 

- (4) If the process has a request_key() authorisation key in its session
-     keyring then:
+ (4) If the process has assumed the authority associated with a request_key()
+     authorisation key then:

 
      (a) If extant, the calling process's thread keyring is searched.
 
 
      (a) If extant, the calling process's thread keyring is searched.
 


@@ -151,7 +191,7 @@ The moment one succeeds, all pending errors are discarded and the found key is
 returned.
 
 Only if all these fail does the whole thing fail with the highest priority
 returned.
 
 Only if all these fail does the whole thing fail with the highest priority

-error. Note that several errors may have come from LSM.
+error.  Note that several errors may have come from LSM.

 
 The error priority is:
 
 
 The error priority is: